How do I terminate the bus wiring…does it just end and you put a wire nut on it, does it have to be looped back on itself? I apologize for these questions but when I went to college all the electrical engineering courses were full so I ended up in business administration.
Just end it. Wire nut would be good.
Right. And it’s a perfectly good question.
Just to add a bit to the previous responses, since - Terminate each of the bus wires individually! Don’t tie them together or anything like that…
Like it has already been said just cap the ends off however you see fit. Do not cap them off together and DO NOT loop them back to the command station. This causes the signals to leave the command station in 2 different directions and arrive some times to the device at different times causing confusion in the device and also if the command station gets feedback throug the track bus then those signals would also return to command station at different times. The times we are talking about are miliseconds but if the offset is right that could turn a 1 into a 0 or visa-versa.
Massey
Actually there seems to be a different opinion on this question. See the following link http://www.wiringfordcc.com/track_2.htm#problem_blown. Should take you to a section called blown decoders (unterminated bus ends). If you scroll down aways you’ll see a simple connecting circuit.
I am not saying this is necessary, or that it applies to OPs question, or that it actually means diddly. I’m only pointing it out because I happen to have read it one time.
Regards
You shouldn’t loop a throttle bus, but it’s perfectly acceptable to loop the track bus. Proof is in all the oval/circle/otherwise looped layouts operating just fine.
The “ringing” described in that writeup, and addressed by the bus termination circuits described there, usually only affect bus runs of about 30 feet or more, and it seems to affect some DCC systems more than others.
For example, my longest bus run is about 22 - 24 feet, and I’ve never experienced any of the blown decoder or erratic operation effects that are symptomatic of bus ringing.
So many users will not need to add those terminator/snubber circuits. But on the other hand, they probably won’t hurt, either, so if you think they may resolve an issue you’re seeing go ahead and add them.
Thank you for the correction, yes the thottle bus is what I ment. The track bus is usually a loop anyway in some cases.
Massey
Using an RF filter on the ends of the bus wires would help eliminate any stray RF that the bus would pick up. Using a capacitor in the circuit you dont actually create a short but it will allow any stray voltages to be eaten up by the resistor with out effecting the main supply current. I like the idea. I need to find a scope and check my layout out and see what it’s waveform looks like. I have 3 power districts and one reversing section I imagine that there may be some stray RF on my rails.
Massey
I’ve never had an issue with the ends of my bus wire just tied together (in a knot, to the last tie-down, NOT electrically, that would be a short). No use of a snubber circuit or anything. My layout’s only about 10x15 though. However, the club modular layout is over 100 feet long when all modules are used, and we have no snubbers there either, and there are no issue with loss of control or worse, it all works just fine. The snummber circuit and the need for bus termination seems mostly needed for NCE PowerPro systems, they constantly talk about it on their Yahoo group.
–Randy
Do you have each power district isolated , with a toggle switch to shut off the one district, if there is a short? Do you have an automatic reverse module to control the polarity? I use #16 wire for my bus wires and #20 wire for feeders every three feet on my 24’x24’ around the room garage loft layout. Bob Hahn
Huh? Track bus is NOT a loop! What is a throttle bus? Digitrax loconet perhaps?
A throttle bus is simply the mechanism by which DCC devices within a given architecture communicate with each other.
So yes, Digitrax’s LocoNet is one type of throttle bus, but it’s certainly not the only one. NCE throttles/devices plug into an NCE throttle bus, Lenz throttles/devices plug into an Lenz throttle bus, and so on…
Thanks for that! I’m guessing that that shouldn’t loop either?
From reading the documentation that comes with the Lenz system, I learned that the throttle bus should be terminated with a resistor. They even supply the appropriate resistor. So, when I added a long throttle bus and a bunch of jacks and it didn’t work, I knew pretty quickly what step I’d left out.
Note that this is a Lenz system. Different rules apply in different sports, so you may not want to do this with a different brand.
Loconet should NEVER loop back on itself. For one thing, if the proper cables are used, looping it back on itself will actually cause a dead short on the Railsync pair of wires.
The track bus - it doesn’t matter. If it mattered, a basic oval layout would never work on DCC because guess what, it loops back on itself! Now, it is completley unecessary and a waste to run bus wires BACK from the far end of a linear layotu just to close the loop, that serves no purpose other than to waste wire. But if your layotu is round and not too large, unless you split the track with insulated joiners it doesn’t matter if the bus completes a circle or not, the track it’s connected to does. On a larger looping layout, say around the walls of a room, the best way to arrange the bus wires is to go equally around in each direction, keeping the distance from the power source to a minimum by having it in the middle of the overall bus run… On a REALLY bg layout, say the bus run woudl be 150 feet, it’s usually best to distribute the boosters, in this case 50 feet from each end, that would make the maximum distance from any booster no more than 50 feet, and of course the bus would be NOT conected between the two sections, plus the track needs to be double gapped at that point as well.
–50 ft — booster 1 -----50 ft ------||-------50ft-----booster 2----50ft----
like that.
–Randy
I just attached my last pair of feeder wires to the ends of the bus.
Brent[C):-)]
For the track bus, I’d crimp a ring lug on each wire, then screw each in turn to the nearest wooden structural member. About an inch of separation between wires ought to do it.
I thank all of you for your input…appears I’m off to the hardware store for wire nuts.